The neonatal Fc receptor (FcRn) is a MHC class I-like molecule that is known to bind IgG at acidic, but not basic pH. As such, FcRn protects IgG from degradation, mediates the bidirectional transport of IgG and IgG/antigen complexes across polarized epithelial cells, and functions in IgG-dependent antigen presentation within dendritic cells. FcRn has also been found to bind albumin in a manner that does not overlap with its binding to IgG, and similarly protects albumin from degradation (Chaudhury et al., Biochemistry 2006, 45:4983-4990).